First, the rice…
For really good premium Sake we use only specially bred Sake rice varieties with extra large cores that contain lots of pure starch. A very desirable feature of these rice-types is that impurities such as unwanted fats or proteins that would negatively affect the taste collect in the outer layers of the corn. Thus, by simply polishing away these layers we gain a super-pure raw material for making our fine Sake! generally, the more of the outer layers are polished away the softer, milder, and increasingly pure and elegant the Sake becomes!
Then the water…
As in every brewing process, the water is extremely important – we need it for washing and soaking of the rice prior to fermentation, and, of course, as a major element of the fermentation process itself. Over the centuries, Sake breweries typically located precisely where they could find ‘good’ wate, and even now these breweries are literally built around that well!
‘Bad’ water contains much iron and mangan, which tend to color the Sake and affect the taste. ‘Good’ water, on the other hand, contains a lot of potassium, magnesium und phosphoric acid, which support the effects of Yeast and Koji (see below) in the brewing process!
…and finally, Yeast & Koji
As in the beer or wine production, Yeast is an integral element in the fermentation process, as it is responsible for converting sugar into alcohol and carbon dioxide. Yet, for Sake, this process is not as straightforward because our Sake rice does not contain any sugar in its natural state. Therefore, as for beer, we first need to subject the Sake to a process of saccarification – for that, we bring polished steamed rice in contact with a very special mold called aspergillus oryzae, a.k.a. ‘KOJI’. Over the course of a few days, Koji penetrates into the rice and converts the starch into sugar, thus allowing the Yeast to start doing its job.